Simply, there are four main versions of master cylinders.  Single bowl, double bowl for all drum brakes, double bowl for disc/drum and double bowl for all discs.  This is a simplified accounting.

The single bowl and  double bowl for all drums have built in residual pressure valves.  The other two do not and residual pressure and proportioning is handled by what is called the combination valve, that hunk of brass near the master cylinder that all the brake lines go to. I haven't had any experience with an all disc system, I assume a proportioning valve is not required??

One of the problems with converting a single bowl to a double is the travel length of the brake pedal.  Too little travel length may result in the failure of the master to actually work  as its supposed to as far as the separate brake safety system. I heard about this issue through the TBird sites I read.  Repositioning the plunger rod on the brake pedal arm supposedly cured this problem.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

charley  is right on,dual master cyls are not all the same . one for disc front ,drum rear are not the same for discs all 4. for all 4 ther is no residual unless the master is under the floor.  no discs residual  front and back 
so do not just throw on a dual without extensive re search

The "safety" feature is definitely more complicated than simply adding a dual master cylinder.  I know this because a failure of a flare in the rear brake circuit of mine resulted in no brakes.  I'm fortunate that It was in my driveway when this happened.  I don't have the answer why that is.  There seems to be a lot of misinformation, misunderstanding and contradiction about brakes even among manufacturers and I have not figured out the truth.  Bottom line, don't let a dual mc give you a false sense of security.


Lawrenceville, GA

I thought, dual reservoir means two separate systems. If other breaks, other will work.
And Residual Pressure Valve keeps only a little bit minimum pressure in the line so shoes are closer to drum.
Works fine without the valve like the original one.


Hyvinkää, FI

why would you go to a dual master,unless you install the valving that shuttles when theirs a leak front or rear. other wise its a wast of time and money.
if you convert to front dishes then it would make sense ,re prev. quote.

I dont know, car has scrapped years ago, but those eigthties STW's was mostly imported (your export, our import) somewhere in '89 in Finland because there was loophole in taxation law. That why here is still a lot of big american STW's in Finland without rear seat paddings.




Hyvinkää, FI

It must have been an Export to Finland. Rock Auto only shows Master Cylinders for Front Disc Brake.

  

Me too.  Ford changed over to front discs in the 65-68 time frame.  My 68 Torino was the first year it was standard equipment on that size car if I remember correctly.





54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Surprised that the 81 had Drum Brakes. Anyway that's why it works on your 59.

  

My Colony Park had drums on all wheels and that master cylinder works fine on 59 Ford. :/
I still have those drums somewhere in safe.
Brake lines are at wrong side off master cylinder (engine side) but that's doesnt matter to me.


Hyvinkää, FI